Extended-life settable compositions comprising red mud

ABSTRACT

A method for using an extended-life settable composition is disclosed. The method includes providing an extended-life settable composition comprising red mud, calcium hydroxide, water, and a cement set retarder. The method further includes activating the extended-life settable composition. The method additionally includes introducing the extended-life settable composition into a subterranean formation and allowing the extended-life settable composition to set in the subterranean formation.

BACKGROUND

Extended-life settable compositions are provided and, more particularly,extended-life settable compositions are provided that comprise red mudand water.

Settable compositions may be used in a variety of subterraneanoperations. For example, in subterranean well construction, a pipestring (e.g., casing, liners, expandable tubulars, etc.) may be run intoa wellbore and cemented in place. The process of cementing the pipestring in place is commonly referred to as “primary cementing.” In atypical primary cementing method, a settable composition may be pumpedinto an annulus between the walls of the wellbore and the exteriorsurface of the pipe string disposed therein. The settable compositionmay set in the annular space, thereby forming a hardened, substantiallyimpermeable annular sheath that may support and position the pipe stringin the wellbore and may bond the exterior surface of the pipe string tothe subterranean formation. Among other things, the annular sheathsurrounding the pipe string prevents the migration of fluids in theannulus and protects the pipe string from corrosion. Settablecompositions may also be used in remedial cementing methods to sealcracks or holes in pipe strings or annular sheaths, to seal highlypermeable formation zones or fractures, or to place a cement plug andthe like.

A broad variety of settable compositions have been used in subterraneancementing operations. In some instances, extended-life settablecompositions have been used. In contrast to conventional settablecompositions that set and hard upon preparation, extended-life settablecompositions are characterized by being capable of remaining in apumpable fluid state for at least about one day (e.g., about 7 days,about 2 weeks, about 2 years or more) at room temperature (e.g., about80° F.) in storage. When desired for use, the extended-life settablecompositions should be capable of activation and consequently developreasonable compressive strengths. For example, an extended-life settablecomposition that is activated may set into a hardened mass. Among otherthings, extended-life settable compositions may be suitable for use inwellbore applications such as applications where it is desirable toprepare the settable composition in advance. This may allow the settablecomposition to be stored prior to use. In addition, this may allow thesettable composition to be prepared at a convenient location beforetransportation to the job site. Accordingly, capital expenditures may bereduced due to a reduction in the need for on-site bulk storage andmixing equipment. This may be particularly useful for offshore cementingoperations where space onboard the vessels may be limited.

While extended-life cement compositions have been developed heretofore,challenges exist with their successful use in subterranean cementingoperations. For example, some extended-life settable compositions mayhave limited use at lower temperatures as they may not developsufficient compressive strength when used in subterranean formationshaving lower bottom hole static temperatures. In addition, it may beproblematic to activate some extended-life settable compositions whilemaintaining acceptable thickening times and compressive strengthdevelopment. Moreover, supply/inventory constraints may restrict theavailability of certain key components of extended-life settablecompositions depending on geographic availability.

BRIEF DESCRIPTION OF THE DRAWINGS

These drawings illustrate certain aspects of some of the embodiments ofthe present method, and should not be used to limit or define themethod.

FIG. 1 illustrates a system for preparation and delivery of anextended-life settable composition to a wellbore in accordance withcertain embodiments.

FIG. 2 illustrates surface equipment that may be used in placement of anextended-life settable composition in a wellbore in accordance withcertain embodiments.

FIG. 3 illustrates placement of an extended-life settable compositioninto a wellbore annulus in accordance with certain embodiments.

FIG. 4 illustrates the particle size distribution for a sample of redmud.

DETAILED DESCRIPTION

Extended-life settable compositions are provided and, more particularly,extended-life settable compositions are provided that comprise red mudand water. The extended-life settable compositions may have desirablerheological properties allowing them to be stored on the surface for anextended period of time and subsequently activated prior to pumpingdownhole. One of the many potential advantages to these compositions isthat an effective use for red mud may be provided thus minimizing theamount of the waste being deposited in disposal sites, such ascontainment reservoirs. Another potential advantage of these methods andcompositions is that the cost of subterranean operations may be reducedby replacement of higher cost additives (e.g., Portland cement, pumice,etc.) with the red mud. Yet another potential advantage of thesecompositions is that the extended-life settable compositions whenactivated may provide a settable composition with sufficient strengthfor use in wellbore applications, such as primary and remedialcementing, among others. Yet another potential advantage is that red mudmay be readily available in certain geographic locations where other theinventory/availability of other components of extended-life settablecompositions may be limited.

The settable component included in the extended-life settablecompositions may comprise red mud. The red mud may be obtained from therefining of bauxite ore using the Bayer process in which bauxite ore isdigested by sodium hydroxide followed by filtration of the solidimpurities. The mixture of solid impurities is known as “red mud,” andit is removed from the other products of the Bayer process. Red mud mayalso be known as “bauxite refinery residue.” As used herein, the term“red mud” refers to a waste/by-product produced when bauxite is refinedusing the Bayer process to produce alumina. A typical alumina plant mayproduce one to two times as much red mud as alumina. Red mud hastypically been considered an undesirable by-product that can add coststo the production of alumina as well as environmental concernsassociated with its disposal. Currently, red mud is typically held indisposal sites such as landfills, retention ponds, or left exposed inpiles on the surface. The term “red mud,” as used herein, is alsointended to encompass red mud solids that have been processed orstabilized in some manner, such as by drying, for example.

The red mud may be provided in any suitable form, including as drysolids or in a liquid form, which may comprise red mud solids and anaqueous based fluid. The settable component comprises the red mud. Theaqueous based fluid content of the red mud may be as high as 25% byweight of the red mud or potentially even higher. If desired, the redmud may be dried to reduce its water content prior to use. Natural ormechanical means may be used for drying the red mud. By way of example,the red mud may be air dried or drum dried.

While the chemical analysis of red mud will typically vary from variousmanufacturers depending on a number of factors, including the particularsolid material feed, process conditions, treatments, and the like, redmud typically may comprise a mixture of solid and metallic oxide-bearingminerals. By way of example, the red mud may comprise a number ofdifferent oxides (based on oxide analysis), including, withoutlimitation, Na₂O, MgO, Al₂O₃, SiO₂, CaO, and/or Fe₂O₃. Moreover, the redmud generally may comprise a number of different crystal structures,including, without limitation, calcite (CaCO₃), quartz (SiO₂), hematite(Fe₂O₃), hauyne (Na₃CaAl₃Si₃O₁₂(SO₄)₂), kaolinite (Al₂Si₂O₅(OH)₄), etc.The majority of red mud may be calcite and quartz with lesser amounts ofhematite, kaolinite, hauyne, etc. The composition of red mud isdiscussed further in Example 1 below.

The red mud may serve as a low cost cement substitute in extended-lifesettable compositions. Red mud may have pozzolanic activity such thatthe red-mud may react with calcium hydroxide in the presence of water.As will be appreciated, calcium hydroxide may be provided in theextended-life settable compositions.

The red mud may be included in the extended-life settable compositionsin a crushed, ground, powder, or other suitable particulate form. Thered mud may comprise particles with a particle size in a range of lessthan 1 μm to over 1000 μm. The median particle size of red mud may bebetween 1 μm and 200 μm. For example, a d50 particle size distributionof from about 1 μm to about 200 μm and, alternatively, from about 10 μmto about 50 μm. By way of further example, the red mud may have a d50particle size distribution ranging between any of and/or including anyof about 1 μm, about 5 μm, about 10 μm, about 20 μm, about 30 μm, about40 μm, about 50 μm, about 60 μm, about 70 μm, about 80 μm, about 90 μm,about 100 μm about 150 μm, or about 200 μm. Further the red mud maycomprise particles with particle diameters less than 3 μm. In someexamples, the red mud may have a multi-modal particle size distribution.By way of example, the red mud may have 2, 3, 4, 5, 6, or more modalpeaks. Modal peaks occur on a particle size distribution curve whenthere are increased particle concentrations relative to particle sizeson either side of the curve. The particles size distribution of red mudis discussed in more detail below in Example 2. One of ordinary skill inthe art, with the benefit of this disclosure, should be able to selectan appropriate particle size for the red mud for a particularapplication.

The red mud may be included in the extended-life settable compositionsin an amount suitable for a particular application. For example, the redmud may be included in the extended-life settable compositions in anamount in the range of from about 50% to about 90% by weight of theextended-life settable composition. By way of further example, the redmud may be present in an amount ranging between any of and/or includingany of about 50%, about 55%, about 65%, about 70%, about 75%, about 80%,about 85%, or about 90% by weight of the extended-life settablecomposition. In a particular example, the red mud may be present in anamount of about 50% to about 80% by weight of the extended-life settablecomponent. One of ordinary skill in the art, with the benefit of thisdisclosure, should recognize the appropriate amount of the red mud toinclude for a chosen application.

Calcium hydroxide, also known as “hydrated lime,” may be present in theextended-life settable compositions. In some embodiments, the calciumhydroxide may be provided as quicklime (calcium oxide) which hydrateswhen mixed with water to form the calcium hydroxide. The calciumhydroxide may be included in embodiments of the set-delayed cementcompositions, for example, to form a hydraulic composition with the redmud. For example, the calcium hydroxide may be included in a redmud-to-calcium hydroxide weight ratio of about 10:1 to about 1:1 or 3:1to about 5:1. Where present, the calcium hydroxide may be included inthe extended-life settable compositions in an amount in the range offrom about 10% to about 100% by weight of the red mud. The calciumhydroxide may be present in an amount ranging between any of and/orincluding any of about 10%, about 20%, about 40%, about 60%, about 80%,or about 100% by weight of the red mud. One of ordinary skill in theart, with the benefit of this disclosure, will recognize the appropriateamount of calcium hydroxide to include for a chosen application.

The extended-life settable composition may not further comprise ahydraulic cement or other cementitious component. In other words, theextended life settable composition may be free of any additionalcementitious components other than the red mud. These varieties ofhydraulic cements may include cements comprising calcium, aluminum,silicon, oxygen, iron, and/or sulfur, which set and harden by reactionwith water. Specific examples may include, but are not limited to,Portland cements, pozzolana cements, gypsum cements, high aluminacontent cements, silica cements, and any combination thereof. Thecementitious components present in the extended-life settablecompositions may consist essentially of the red mud. For example, thecementitious components may comprise the red mud without any additionalcomponents (e.g., Portland cement, fly ash, slag cement) thathydraulically set in the presence of water.

The extended-life settable composition may further comprise a cement setretarder. A broad variety of cement set retarders may be suitable foruse. For example, the cement set retarder may comprise phosphonic acids,such as ethylenediamine tetra(methylene phosphonic acid),diethylenetriamine penta(methylene phosphonic acid), etc.;lignosulfonates, such as sodium lignosulfonate, calcium lignosulfonate,etc.; salts such as stannous sulfate, lead acetate, monobasic calciumphosphate, organic acids, such as citric acid, tartaric acid, etc.;cellulose derivatives such as hydroxyl ethyl cellulose (HEC) andcarboxymethyl hydroxyethyl cellulose (CMHEC); synthetic co- orter-polymers comprising sulfonate and carboxylic acid groups such assulfonate-functionalized acrylamide-acrylic acid co-polymers; boratecompounds such as alkali borates, sodium metaborate, sodium tetraborate,potassium pentaborate; derivatives thereof, or mixtures thereof.Examples of suitable cement set retarders include, among others,phosphonic acid derivatives. One example of a suitable cement setretarder is Micro Matrix® cement retarder, available from HalliburtonEnergy Services, Inc., Houston, Tex. Generally, the cement set retardermay be present in the extended-life settable composition in an amountsufficient to delay setting for a desired time. The cement set retardermay be present in the extended-life settable composition in an amount inthe range of from about 0.01% to about 10% by weight of the red mud.More particularly, the cement set retarder may be present in an amountranging between any of and/or including any of about 0.01%, about 0.1%,about 1%, about 2%, about 4%, about 6%, about 8%, or about 10% by weightof the red mud. One of ordinary skill in the art, with the benefit ofthis disclosure, should recognize the appropriate amount of the cementset retarder to include for a chosen application.

The extended-life settable compositions may optionally comprise adispersant. Examples of suitable dispersants may include, withoutlimitation, sulfonated-formaldehyde-based dispersants (e.g., sulfonatedacetone formaldehyde condensate), examples of which may include Daxad®19 dispersant available from Geo Specialty Chemicals, Ambler, Pa. Othersuitable dispersants may be polycarboxylated ether dispersants such asLiquiment® 5581F and Liquiment® 514L dispersants available from BASFCorporation Houston, Tex.; or Ethacryl™ G dispersant available fromCoatex, Genay, France. An additional example of a suitable commerciallyavailable dispersant is CFR™-3 dispersant, available from HalliburtonEnergy Services, Inc., Houston, Tex. The Liquiment® 514L dispersant maycomprise 36% by weight of the polycarboxylated ether in water. While avariety of dispersants may be used, some dispersants may be preferredfor use with certain cement set retarders. For example, if anextended-life settable composition comprises a phosphonic acidderivative cement set retarder, a polycarboxylated ether dispersant maybe preferable. Without being limited by theory, it is believed thatpolycarboxylated ether dispersants may synergistically interact withphosphonic acid derivative cement set retarders resulting in formationof a gel that suspends the red mud in the composition for an extendedperiod of time. One of ordinary skill in the art, with the benefit ofthis disclosure, should recognize the appropriate type of dispersant toinclude for a chosen application.

The dispersant may be included in the extended-life settablecompositions in an amount in the range of from about 0.01% to about 5%by weight of the red mud. More particularly, the dispersant may bepresent in an amount ranging between any of and/or including any ofabout 0.01%, about 0.1%, about 0.5%, about 1%, about 2%, about 3%, about4%, or about 5% by weight of the red mud. One of ordinary skill in theart, with the benefit of this disclosure, will recognize the appropriateamount of dispersant to include for a chosen application.

The extended-life cement compositions may comprise water. The water maybe from any source provided that it does not contain an excess ofcompounds that may undesirably affect other components in theextended-life settable compositions. The water may comprise fresh wateror salt water. Salt water generally may include one or more dissolvedsalts therein and may be saturated or unsaturated as desired for aparticular application. Seawater or brines may be suitable for use insome applications. Further, the water may be present in an amountsufficient to form a pumpable slurry. In certain embodiments, the watermay be present in the extended-life settable compositions in an amountin the range of from about 33% to about 200% by weight of the red mud.In certain embodiments, the water may be present in the extended-lifesettable compositions in an amount in the range of from about 35% toabout 70% by weight of the red mud. With the benefit of this disclosureone of ordinary skill in the art should recognize the appropriate amountof water for a chosen application.

Other optional additives suitable for use in subterranean cementingoperations may also be added to the extended-life settable compositionsas deemed appropriate by one of ordinary skill in the art. As desired,these additives may be added prior to, or after, storage of theextended-life settable compositions. Examples of such additives include,but are not limited to, strength-retrogression additives, set weightingagents, lightweight additives, gas-generating additives, mechanicalproperty enhancing additives, lost-circulation materials, defoamingagents, foaming agents, thixotropic additives, and combinations thereof.Specific examples of these, and other, additives include silica (e.g.,crystalline silica, amorphous silica, fumed silica, etc.), salts,fibers, hydratable clays, shale (e.g., calcined shale, vitrified shale,etc.), microspheres, diatomaceous earth, natural pozzolan, resins,latex, combinations thereof, and the like. Other optional additives mayalso be included, including, but not limited to, cement kiln dust, limekiln dust, fly ash, slag cement, shale, zeolite, metakaolin, pumice,perlite, lime, silica, rice husk ash, small-particle size cement,combinations thereof, and the like. A person having ordinary skill inthe art, with the benefit of this disclosure, will be able to determinethe type and amount of additive useful for a particular application anddesired result.

Optionally, strength-retrogression additives may be included inextended-life settable compositions to, for example, prevent theretrogression of strength after the extended-life settable compositionhas been allowed to develop compressive strength. These additives mayallow the extended-life settable compositions to form as intended,preventing cracks and premature failure of the extended-life settablecomposition. Examples of suitable strength-retrogression additives mayinclude, but are not limited to, amorphous silica, coarse graincrystalline silica, fine grain crystalline silica, or a combinationthereof.

Optionally, weighting agents may be included in the extended-lifesettable compositions. Weighting agents are typically materials thatweigh more than water and may be used to increase the density of theextended-life settable compositions. By way of example, weighting agentsmay have a specific gravity of about 2 or higher (e.g., about 2, about4, etc.). Examples of weighting agents that may be used include, but arenot limited to, hematite, hausmannite, and barite, and combinationsthereof. Specific examples of suitable weighting agents includeHI-DENSE® weighting agent, available from Halliburton Energy Services,Inc.

Optionally, lightweight additives may be included in the extended-lifesettable compositions to, for example, decrease the density of theextended-life settable compositions. Examples of suitable lightweightadditives include, but are not limited to, bentonite, coal, diatomaceousearth, expanded perlite, fly ash, gilsonite, hollow microspheres,low-density elastic beads, nitrogen, pozzolan-bentonite, sodiumsilicate, combinations thereof, or other lightweight additives known inthe art.

Optionally, gas-generating additives may be included in theextended-life settable compositions to release gas at a predeterminedtime, which may be beneficial to prevent gas migration from theformation through the extended-life settable composition before ithardens. The generated gas may combine with or inhibit the permeation ofthe extended-life settable composition by formation gas. Examples ofsuitable gas-generating additives include, but are not limited to, metalparticles (e.g., aluminum powder) that react with an alkaline solutionto generate a gas.

Optionally, mechanical-property-enhancing additives may be included inthe extended-life settable compositions to, for example, ensure adequatecompressive strength and long-term structural integrity. Theseproperties can be affected by the strains, stresses, temperature,pressure, and impact effects from a subterranean environment. Examplesof mechanical property enhancing additives include, but are not limitedto, carbon fibers, glass fibers, metal fibers, mineral fibers, silicafibers, polymeric elastomers, and latexes.

Optionally, lost-circulation materials may be included in embodiments ofthe extended-life settable compositions to, for example, help preventthe loss of fluid circulation into the subterranean formation. Examplesof lost-circulation materials include but are not limited to, cedarbark, shredded cane stalks, mineral fiber, mica flakes, cellophane,calcium carbonate, ground rubber, polymeric materials, pieces ofplastic, grounded marble, wood, nut hulls, plastic laminates (Formica®laminate), corncobs, and cotton hulls.

Optionally, defoaming additives may be included in the extended-lifesettable compositions to, for example, reduce tendency for theextended-life settable slurries to foam during mixing and pumping of theextended-life settable slurries. Examples of suitable defoamingadditives include, but are not limited to, polyol silicone compounds.Suitable defoaming additives are available from Halliburton EnergyServices, Inc., under the product name D-AIR™ defoamers.

Optionally, foaming additives (e.g., foaming surfactants) may beincluded to, for example, facilitate foaming and/or stabilize theresultant foam formed therewith. Examples of suitable foaming additivesinclude, but are not limited to: mixtures of an ammonium salt of analkyl ether sulfate, a cocoamidopropyl betaine surfactant, acocoamidopropyl dimethylamine oxide surfactant, sodium chloride, andwater; mixtures of an ammonium salt of an alkyl ether sulfatesurfactant, a cocoamidopropyl hydroxysultaine surfactant, acocoamidopropyl dimethylamine oxide surfactant, sodium chloride, andwater; hydrolyzed keratin; mixtures of an ethoxylated alcohol ethersulfate surfactant, an alkyl or alkene amidopropyl betaine surfactant,and an alkyl or alkene dimethylamine oxide surfactant; aqueous solutionsof an alpha-olefinic sulfonate surfactant and a betaine surfactant; andcombinations thereof. An example of a suitable foaming additive isZONESEALANT™ 2000 agent, available from Halliburton Energy Services,Houston, Tex.

Optionally, thixotropic additives may be included in the extended-lifesettable compositions to, for example, provide an extended-life settablecomposition that may be pumpable as a thin or low viscosity fluid, andwhen allowed to remain quiescent attains a relatively high viscosity.Among other things, thixotropic additives may be used to help controlfree water, create rapid gelation as the slurry sets, combat lostcirculation, prevent “fallback” in annular column, and minimize gasmigration. Examples of suitable thixotropic additives include, but arenot limited to, gypsum, water soluble carboxyalkyl, hydroxyalkyl, mixedcarboxyalkyl hydroxyalkyl either of cellulose, polyvalent metal salts,zirconium oxychloride with hydroxyethyl cellulose, or a combinationthereof.

Those of ordinary skill in the art will appreciate that embodiments ofthe extended-life settable compositions generally should have a densitysuitable for a particular application. By way of example, theextended-life settable compositions may have a density in the range offrom about 4 pounds per gallon (“ppg”) to about 20 ppg. In certainembodiments, the extended-life settable compositions may have a densityin the range of from about 8 ppg to about 17 ppg. Embodiments of theextended-life settable compositions may be foamed or unfoamed or maycomprise other means to reduce their densities, such as hollowmicrospheres, low-density elastic beads, or other density-reducingadditives known in the art. In embodiments, the density may be reducedafter storage, but prior to placement in a subterranean formation. Inembodiments, weighting additives may be used to increase the density ofthe extended-life settable compositions. Examples of suitable weightingadditives may include barite, hematite, hausmannite, calcium carbonate,siderite, ilmenite, or combinations thereof. In particular embodiments,the weighting additives may have a specific gravity of 3 or greater.Those of ordinary skill in the art, with the benefit of this disclosure,should recognize the appropriate density for a particular application.

The extended-life settable compositions may have a delayed set in thatthey may be capable of remaining in a pumpable fluid state for at leastone day (e.g., about 1 day, about 2 weeks, about 2 years or more) atroom temperature (e.g., about 80° F.) in storage. For example, theextended-life settable compositions may remain in a pumpable fluid statefor a period of time from about 1 day to about 7 days or more. In someembodiments, the extended-life settable compositions may remain in apumpable fluid state for at least about 1 day, about 7 days, about 10days, about 20 days, about 30 days, about 40 days, about 50 days, about60 days, or longer. A fluid is considered to be in a pumpable fluidstate where the fluid has a consistency of less than 70 Bearden units ofconsistency (“Bc”), as measured on a pressurized consistometer inaccordance with the procedure for determining cement thickening timesset forth in API RP Practice 10B-2, Recommended Practice for TestingWell Cements, First Edition, July 2005.

Cement set activators may be added to the extended-life settablecompositions. Cement set activators may induce and/or accelerate settingand may also activate retarded extended-life settable compositions. Theterm “activate,” as used herein, refers to the activation of a retardedextended-life settable composition and in certain cases may also referto the acceleration of the setting of an extended-life settablecomposition if the mechanism of said activation also accelerates thedevelopment of compressive strength. By way of example, a cement setactivator may be added to an extended-life settable composition toactivate an extended-life settable composition that has been retardedwith a phosphonic acid. Alternatively, an extended-life settablecomposition may be thermally activated, for example, by exposure toelevated temperatures in a well bore. An extended-life settablecomposition that has been activated may set to form a hardened mass in atime period in the range of from about 1 hour to about 12 days. Forexample, embodiments of the extended-life settable compositions may setto form a hardened mass in a time period ranging between any of and/orincluding any of about 1 hour, about 6 hours, about 12 hours, about 1day, about 2 days, about 4 days, about 6 days, about 8 days, about 10days, or about 12 days.

Examples of suitable cement set activators include, but are not limitedto: amines such as triethanolamine, diethanolamine; silicates such assodium silicate; zinc formate; calcium acetate; Groups IA and IIAhydroxides such as sodium hydroxide, magnesium hydroxide, and calciumhydroxide; monovalent salts such as sodium chloride; divalent salts suchas calcium chloride; nanosilica (i.e., silica having a particle size ofless than or equal to about 100 nanometers); polyphosphates; andcombinations thereof. The cement set activator should be added toembodiments of the extended-life settable compositions in amountssufficient to induce the extended-life settable compositions to set intoa hardened mass. In certain embodiments, the cement set activator may beadded to an extended-life settable composition in an amount in the rangeof about 1% to about 20% by weight of the red mud. In specificembodiments, the cement set activator may be present in an amountranging between any of and/or including any of about 1%, about 5%, about10%, about 15%, or about 20% by weight of the red mud. One of ordinaryskill in the art, with the benefit of this disclosure, will recognizethe appropriate amount of cement set activator to include for a chosenapplication.

The extended-life settable compositions may set to have a desirablecompressive strength after activation. Compressive strength is generallythe capacity of a material or structure to withstand axially directedpushing forces. The compressive strength may be measured at a specifiedtime after the activation of the extended-life settable compositionswhile the extended-life settable composition is maintained underspecified temperature and pressure conditions. Compressive strength canbe measured by either destructive or non-destructive methods. Thedestructive method physically tests the strength of treatment fluidsamples at various points in time by crushing the samples in acompression-testing machine. The compressive strength is calculated fromthe failure load divided by the cross-sectional area resisting the loadand is reported in units of pound-force per square inch (psi).Non-destructive methods may employ a UCA™ Ultrasonic Cement Analyzer,available from Fann Instrument Company, Houston, Tex. Compressivestrength values may be determined in accordance with API RP 10B-2,Recommended Practice for Testing Well Cements, First Edition, July 2005.

By way of example, extended-life settable compositions may develop a24-hour compressive strength in the range of from about 50 psi to about500 psi, alternatively, from about 100 psi to about 400 psi, oralternatively from about 200 psi to about 300 psi. In particular, theextended-life settable compositions may develop a compressive strengthin 24 hours of at least about 50 psi, at least about 100 psi, at leastabout 200 psi, or more. The compressive strength values may bedetermined using destructive or non-destructive methods at anytemperature.

In some examples, the extended-life settable compositions may havedesirable thickening times. Thickening time typically refers to the timea fluid, such as an extended-life settable composition, remains in afluid state capable of being pumped. A number of different laboratorytechniques may be used to measure thickening time. A pressurizedconsistometer, operated in accordance with the procedure set forth inthe aforementioned API RP Practice 10B-2, may be used to measure whethera fluid is in a pumpable fluid state. The thickening time may be thetime for the treatment fluid to reach 70 Bc and may be reported as thetime to reach 70 Bc. The extended-life settable compositions may havethickening times greater than about 1 hour, alternatively, greater thanabout 2 hours, greater than about 15 hours, greater than about 30 hours,greater than about 100 hours, or alternatively greater than about 190hours at 3,000 psi and temperatures in a range of from about 50° F. toabout 400° F., alternatively, in a range of from about 70° F. to about140° F., and alternatively at a temperature of about 100° F.

As will be appreciated by those of ordinary skill in the art, theextended-life settable compositions may be used in a variety ofsubterranean operations, including primary and remedial cementing. Forexample, an extended-life settable composition may be provided thatcomprises red mud, calcium hydroxide, water, a cement set retarder, andoptionally a dispersant. A cement set activator may be added to theextended-life settable composition to activate the extended-lifesettable composition prior to being pumped downhole where it may beintroduced into a subterranean formation and allowed to set therein. Asused herein, introducing the extended-life settable composition into asubterranean formation includes introduction into any portion of thesubterranean formation, including, without limitation, into a wellboredrilled into the subterranean formation, into a near wellbore regionsurrounding the wellbore, or into both.

Additional applications may include storing extended-life settablecompositions. For example, an extended-life settable composition may beprovided that comprises red mud, calcium hydroxide, water, a cement setretarder, and optionally a dispersant. The extended-life settablecomposition may be stored in a vessel or other suitable container. Theextended-life settable composition may be stored and then activatedprior to or while pumping downhole. The extended-life settablecomposition may be permitted to remain in storage for a desired timeperiod. For example, the extended-life settable compositions may remainin storage for a time period of about 1 day, about 2 weeks, about 2years, or longer. For example, the extended-life settable compositionmay remain in storage for a time period of about 1 day, about 2 days,about 5 days, about 7 days, about 10 days, about 20 days, about 30 days,about 40 days, about 50 days, about 60 days, or up to about 2 years.When desired for use, the extended-life settable composition may beactivated by addition of a cement set activator, introduced into asubterranean formation, and allowed to set therein.

In primary cementing applications, for example, an extended-lifesettable composition may be introduced into an annular space between aconduit located in a wellbore and the walls of a wellbore (and/or alarger conduit in the wellbore), wherein the wellbore penetrates thesubterranean formation. The extended-life settable composition may beallowed to set in the annular space to form a hardened annular sheath.The extended-life settable composition may form a barrier that preventsthe migration of fluids in the wellbore. The extended-life settablecomposition may also, for example, support the conduit in the wellbore.

In remedial cementing applications, the extended-life settablecompositions may be used, for example, in squeeze-cementing operationsor in the placement of plugs. By way of example, the extended-lifesettable compositions may be placed in a wellbore to plug an opening(e.g., a void or crack) in the formation, in a gravel pack, in theconduit, in the annular sheath, and/or between the annular sheath andthe conduit (e.g., a microannulus).

A method may be provided. The method may be used in conjunction with oneor more of the methods, compositions, and/or systems illustrated inFIGS. 1-3. The method may comprise providing an extended-life settablecomposition comprising red mud, calcium hydroxide, water, and a cementset retarder; activating the extended-life settable composition;introducing the extended-life settable composition into a subterraneanformation; and allowing the extended-life settable composition to set inthe subterranean formation. The red mud may be an insoluble residue fromextraction of alumina from bauxite ore. The water may be present in theextended-life settable composition in an amount of at least 40% byweight of the red mud, and the calcium hydroxide may be present in theextended-life settable composition in an amount of at least 10% byweight of the red mud. The red mud may be provided from source of redmud having a water content up to 25% by weight of the red mud. The redmud may comprise at least 20% calcite. The cement set retarder may beselected from the group consisting of a phosphonic acid, a phosphonicacid derivative, a lignosulfonate, a salt, an organic acid, a cellulosederivative, a synthetic co- or ter-polymer comprising sulfonate andcarboxylic acid groups, a borate compound, and any combination thereof.The extended-life settable composition may further comprise adispersant. The cement set retarder may comprise a phosphonic acidderivative. The extended-life settable composition may comprise apolycarboxylated ether dispersant. The extended-life settablecomposition may be stored for a period of about 1 day or longer prior tothe step of introducing the cement composition into the subterraneanformation. The step of activating the extended-life settable compositionmay comprise adding a cement set activator to the extended-life settablecomposition. The step of introducing the extended-life settablecomposition may comprise pumping the extended-life settable compositionthrough a feed pipe and into a wellbore annulus.

An extended-life settable composition may be provided. The settablecomposition may be used in conjunction with one or more of the methods,compositions, and/or systems illustrated in FIGS. 1-3. The settablecomposition may comprise red mud; calcium hydroxide; water; and a cementset retarder, wherein the extended-life settable composition is capableof remaining in a pumpable fluid state for about 1 day or longer at 80°F. The red mud may be an insoluble residue from extraction of aluminafrom bauxite ore. The water may be present in the extended-life settablecomposition in an amount of at least 40% by weight of the red mud, andthe calcium hydroxide may be present in the extended-life settablecomposition in an amount of at least 10% by weight of the red mud. Thered mud may be provided from source of red mud having a water content upto 25% by weight of the red mud. The red mud may comprise at least 20%calcite. The cement set retarder may be selected from the groupconsisting of a phosphonic acid, a phosphonic acid derivative, alignosulfonate, a salt, an organic acid, a cellulose derivative, asynthetic co- or ter-polymer comprising sulfonate and carboxylic acidgroups, a borate compound, and any combination thereof. Theextended-life settable composition may further comprise a dispersant.The cement set retarder may comprise a phosphonic acid derivative. Theextended-life settable composition may comprise a polycarboxylated etherdispersant.

A system may be provided. The system may be used in conjunction with oneor more of the methods, compositions, and/or systems illustrated onFIGS. 1-3. The system may comprise an extended-life settable compositionthat is capable of remaining in a pumpable fluid state for about 1 dayor longer at 80° F.; wherein the extended-life settable compositioncomprises red mud, calcium hydroxide, water, and a cement set retarder;and a cement set activator for activating and/or accelerating theextended-life settable composition. The system may further comprise avessel containing the extended-life settable composition and a pumpcoupled to the vessel for delivering the extended-life settablecomposition into a wellbore. The red mud may be an insoluble residuefrom extraction of alumina from bauxite ore. The water may be present inthe extended-life settable composition in an amount of at least 40% byweight of the red mud, and the calcium hydroxide may be present in theextended-life settable composition in an amount of at least 10% byweight of the red mud. The red mud may be provided from source of redmud having a water content up to 25% by weight of the red mud. The redmud may comprise at least 20% calcite. The cement set retarder may beselected from the group consisting of a phosphonic acid, a phosphonicacid derivative, a lignosulfonate, a salt, an organic acid, a cellulosederivative, a synthetic co- or ter-polymer comprising sulfonate andcarboxylic acid groups, a borate compound, and any combination thereof.The extended-life settable composition may further comprise adispersant. The cement set retarder may comprise a phosphonic acidderivative. The extended-life settable composition may comprise apolycarboxylated ether dispersant.

Referring now to FIG. 1, preparation of an extended-life settablecomposition will now be described. FIG. 1 illustrates a system 2 for thepreparation of an extended-life settable composition and subsequentdelivery of the composition to a wellbore. As shown, the extended-lifesettable composition may be stored in a vessel 4 and then pumped viapumping equipment 6 to the wellbore. The vessel 4 and the pumpingequipment 6 may be disposed on one or more cement trucks as will beapparent to those of ordinary skill in the art. A cement set activatormay be added to the extended-life settable composition in the vessel 4or may be added to extended-life settable composition as it is beingpumped from the vessel 4. Alternatively, a cement set activator may beadded to an extended-life cement composition after the extended-lifesettable composition has been pumped into the wellbore. In embodimentsthat add the cement set activator to the extended-life settablecomposition as it is being pumped, a jet mixer may be used, for example,to continuously mix the cement set activator and the extended-lifesettable composition as it is being pumped to the wellbore.Alternatively, a re-circulating mixer and/or a batch mixer may be usedto mix the extended-life settable composition and the cement setactivator, and the cement set activator may be added to the mixer as apowder prior to pumping the extended-life settable composition downhole.Additionally, batch mixer type units may be plumbed in line with aseparate vessel containing a cement set activator. The cement setactivator may then be fed in-line with the extended-life settablecomposition as it is pumped out of the vessel 4. There is no preferredmethod for preparing or mixing the extended-life settable compositions,and one having ordinary skill in the art should be readily able toprepare, mix, and pump the extended-life settable compositions using theequipment on hand.

An example technique for placing an extended-life cement compositioninto a subterranean formation will now be described with reference toFIG. 2. FIG. 2 illustrates surface equipment 10 that may be used in theplacement of an extended-life settable composition in accordance withcertain embodiments. It should be noted that while FIG. 2 generallydepicts a land-based operation, those skilled in the art will readilyrecognize that the principles described herein are equally applicable tosubsea operations that employ floating or sea-based platforms and rigs,without departing from the scope of the disclosure. As illustrated byFIG. 2, the surface equipment 10 may include a cementing unit 12, whichmay include one or more cement trucks. The cementing unit 12 may includethe vessel 4 and the pumping equipment 6 shown in FIG. 1 which isrepresented by system 2 on the cementing unit 12, as will be apparent tothose of ordinary skill in the art. The cementing unit 12 may pump anextended-life settable composition 14 through a feed pipe 16 and to acementing head 18 which conveys the extended-life settable composition14 downhole.

Turning now to FIG. 3, placing the extended-life settable composition 14into a subterranean formation 20 will now be described. As illustrated,a wellbore 22 may be drilled into the subterranean formation 20. Whilewellbore 22 is shown extending generally vertically into thesubterranean formation 20, the principles described herein are alsoapplicable to wellbores that extend at an angle through the subterraneanformation 20, such as horizontal and slanted wellbores. As illustrated,the wellbore 22 comprises walls 24. In the illustrated embodiment, asurface casing 26 has been inserted into the wellbore 22. The surfacecasing 26 may be cemented to the walls 24 of the wellbore 22 by cementsheath 28. In the illustrated embodiment, one or more additionalconduits (e.g., intermediate casing, production casing, liners, etc.),shown here as casing 30 may also be disposed in the wellbore 22. Asillustrated, there is a wellbore annulus 32 formed between the casing 30and the walls 24 of the wellbore 22 and/or the surface casing 26. One ormore centralizers 34 may be attached to the casing 30, for example, tocentralize the casing 30 in the wellbore 22 prior to and during thecementing operation.

With continued reference to FIG. 3, the extended-life settablecomposition 14 may be pumped down the interior of the casing 30. Theextended-life settable composition 14 may be allowed to flow down theinterior of the casing 30 through the casing shoe 42 at the bottom ofthe casing 30 and up around the casing 30 into the wellbore annulus 32.The extended-life settable composition 14 may be allowed to set in thewellbore annulus 32, for example, to form an annular sheath thatsupports and positions the casing 30 in the wellbore 22. While notillustrated, other techniques may also be utilized for introduction ofthe extended-life settable composition 14. By way of example, reversecirculation techniques may be used that include introducing theextended-life settable composition 14 into the subterranean formation 20by way of the wellbore annulus 32 instead of through the casing 30.

As it is introduced, the extended-life settable composition 14 maydisplace other fluids 36, such as drilling fluids and/or spacer fluidsthat may be present in the interior of the casing 30 and/or the wellboreannulus 32. At least a portion of the displaced fluids 36 may exit thewellbore annulus 32 via a flow line 38 and be deposited, for example, inone or more retention pits 40 (e.g., a mud pit), as shown on FIG. 2.Referring again to FIG. 3, a bottom plug 44 may be introduced into thewellbore 22 ahead of the extended-life settable composition 14, forexample, to separate the extended-life settable composition 14 from thefluids 36 that may be inside the casing 30 prior to cementing. After thebottom plug 44 reaches the landing collar 46, a diaphragm or othersuitable device should rupture to allow the extended-life settablecomposition 14 through the bottom plug 44. In FIG. 3, the bottom plug 44is shown on the landing collar 46. In the illustrated embodiment, a topplug 48 may be introduced into the wellbore 22 behind the extended-lifesettable composition 14. The top plug 48 may separate the extended-lifesettable composition 14 from a displacement fluid 50 and also push theextended-life settable composition 14 through the bottom plug 44.

The exemplary extended-life settable compositions disclosed herein maydirectly or indirectly affect one or more components or pieces ofequipment associated with the preparation, delivery, recapture,recycling, reuse, and/or disposal of the disclosed extended-lifesettable compositions. For example, the disclosed extended-life settablecompositions may directly or indirectly affect one or more mixers,related mixing equipment, mud pits, storage facilities or units,composition separators, heat exchangers, sensors, gauges, pumps,compressors, and the like used generate, store, monitor, regulate,and/or recondition the exemplary extended-life settable compositions.The disclosed extended-life settable compositions may also directly orindirectly affect any transport or delivery equipment used to convey theextended-life settable compositions to a well site or downhole such as,for example, any transport vessels, conduits, pipelines, trucks,tubulars, and/or pipes used to compositionally move the extended-lifesettable compositions from one location to another, any pumps,compressors, or motors (e.g., topside or downhole) used to drive theextended-life settable compositions into motion, any valves or relatedjoints used to regulate the pressure or flow rate of the extended-lifesettable compositions, and any sensors (i.e., pressure and temperature),gauges, and/or combinations thereof, and the like. The disclosedextended-life settable compositions may also directly or indirectlyaffect the various downhole equipment and tools that may come intocontact with the extended-life settable compositions such as, but notlimited to, wellbore casing, wellbore liner, completion string, insertstrings, drill string, coiled tubing, slickline, wireline, drill pipe,drill collars, mud motors, downhole motors and/or pumps, cement pumps,surface-mounted motors and/or pumps, centralizers, turbolizers,scratchers, floats (e.g., shoes, collars, valves, etc.), logging toolsand related telemetry equipment, actuators (e.g., electromechanicaldevices, hydromechanical devices, etc.), sliding sleeves, productionsleeves, plugs, screens, filters, flow control devices (e.g., inflowcontrol devices, autonomous inflow control devices, outflow controldevices, etc.), couplings (e.g., electro-hydraulic wet connect, dryconnect, inductive coupler, etc.), control lines (e.g., electrical,fiber optic, hydraulic, etc.), surveillance lines, drill bits andreamers, sensors or distributed sensors, downhole heat exchangers,valves and corresponding actuation devices, tool seals, packers, cementplugs, bridge plugs, and other wellbore isolation devices, orcomponents, and the like.

EXAMPLES

To facilitate a better understanding of the present claims, thefollowing examples of certain aspects of the disclosure are given. In noway should the following examples be read to limit, or define, theentire scope of the claims.

Example 1

A sample of red mud was obtained from an alumina manufacturer andsubjected to oxide analysis by EDXRF (Energy Dispersive X-RayFluorescence) which showed the following composition by weight:

TABLE 1 Full Oxide Analysis of Red Mud Oxide Full Oxide (wt %) LossCorrected (wt %) Na₂O 1.19 1.34 MgO 0.07 0.08 Al₂O₃ 17.3 19.47 SiO₂29.77 33.51 SO₃ 0.98 1.1 K₂O 1.18 1.33 CaO 18.27 20.57 P₂O₅ 1.29 1.45TiO₂ 3.09 3.48 Mn₂O₃ 0.33 0.37 Fe₂O₃ 15.31 17.23 ZnO 0.02 0.02 SrO 0.040.05 LOI 11.16 — Moisture Content 22.94

The sample of red mud was subjected to X-ray diffraction analysis withRietveld Full Pattern refinement, which showed the following crystallinematerials present by weight:

TABLE 2 XRD of Red Mud Mineral Empirical Formula Concentration CalciteCaCO₃ 22%  Quartz SiO₂ 30%  Hatrurite C₃S 2% Larnite C₂S 2%Brownmillerite C₄AF trace Hematite Fe₂O₃ 10%  Magnetite Fe₃O₄ 1% KatoiteCa₃Al₂(SiO₄)_(3−x)(OH)_(4x) x = 1.5-3 — Hauyne Na₃CaAl₃Si₃O₁₂(SO₄)₂ 9%Anhydrite CaSO₄ 1% Gibbsite Al(OH)₃ 4% K-feldspar KAlSI₃O₈ 4% KaoliniteAl₂Si₂O₅(OH)₄ 10%  Perovskite CaTiO₃ 5%

As discussed above, red mud has no katoite and is mostly comprised ofcalcite and quartz. These properties distinguish red mud from otherwaste products obtained from bauxite refining (e.g., brown mud).

Example 2

Particle size analysis was performed on a sample of red mud to obtainthe particle size distribution in the sample using a MalvernMastersizer® 3000 laser diffraction particle size analyzer. The particlesize distribution is illustrated in FIG. 4. The particle size analysisillustrates the wide distribution of particle sizes in the red mudsample. The median particle size in the sample was 31.2 μm. 10% of thesample contained material with a particle diameters less than 2.5 μm.10% of the sample also contained material with particle diametersgreater than 333 μm. This wide range of particle sizes may allows thered mud to bridge bigger, wider lost circulation zones as well as smalllost circulation fractures. The synergistic effect from the differentsized particles may provide optimal plugging, bridging, etc. and makesthe red mud ideally suited for use as a lost circulation material. Table3 illustrates the size distributions.

TABLE 3 Particle Size Analysis Particle Size Distribution of Red MudSolid Particles D10 (microns) 2.48 D50 (microns) 31.2 D90 (microns) 333

The density of the sample of the red mud was also determined using aQuantachrome® Ultrapyc 1200. The density was determined before and afterdrying. The sample was dried in a vacuum oven at 180° F. for 24 hours.The density in grams per cubic centimeter is provided in the tablebelow.

TABLE 4 Density Analysis Red Mud Density (g/cc) As received 2.04 Dried2.86

Example 3

A sample extended-life settable composition was prepared to evaluate theuse of red mud as a settable material. To prepare the sampleextended-life cement composition a sample of red mud was mixed withwater, calcium hydroxide, and a dispersant. The sample was split in twoto create two experimental samples. The first experimental sample wasleft neat and no activator/accelerator was added to it. The secondexperimental sample was provided calcium chloride which is believed tofunction as an accelerator. The sample slurries were each prepared bydry blending the red mud, calcim hydroxide, and dispersant. The dryblends were then each added to a blender which contained tap water andblended per API specifications. In these examples, the term “% BWoRM”refers to the percent of each component by weight of the red mud. Table5 illustrates the compositional make-up of the sample slurries.

As discussed above, experimental sample 2 was accelerated by theaddition of a solution of 43% calcium chloride in a sufficient amount toreach a calcium chloride content in experimental sample 2 of 10% BWoRM.After addition of the calcium chloride, each of the experimental sampleswere cured in 1 inch by 2 inch brass cylinders that were placed in waterbaths at 180° F. for 24 hours at atmospheric pressure. Then, thedestructive compress strengths (C.S.) were measured using a mechanicalpress in accordance with the procedure set forth in API RP Practice10B-2, Recommended Practice for Testing Well Cements. The compressivestrength data is presented in Table 5 below. The reported compressivestrengths are an average for two cylinders of each sample slurry. Thedensity of each sample was 13.6 pound per gallon (ppg).

TABLE 5 Sample Composition Experimental Sample 1 2 Component % BWoRM %BWoRM Red Mud 100 100 Water 41.3 41.3 Calcium Hydroxide 20.0 20.0Dispersant 0.38 0.38 CaCl₂ — 10.0 Compressive Strength (psi)Consolidated, <50 234

This experiment thus illustrates that red mud can function as anextended-life settable composition. Thus it may be used in applicationfor extended-life settable compositions and as a replacement materialfor known extended-life settable materials to reduce costs.

Example 4

Additional rheological testing was performed on an extended-lifesettable composition that was retarded and allowed to age for 17 days.To prepare the sample extended-life cement composition a sample of redmud was mixed with water, calcium hydroxide, a cement retarder, a weightadditive, and a dispersant. The cement retarder was MICRO MATRIX® cementretarder available from Halliburton Energy Services, Inc. of Houston,Tex. The weight additive was MICROMAX® weight additive available fromHalliburton Energy Services, Inc. of Houston, Tex. The dispersant wasLIQUIMENT® 5581 F available from BASF SE of Houston, Tex. The sample wasprepared by dry blending the red mud, calcium hydroxide, cementretarder, weight additive, and dispersant. The dry blend was then addedto a blender which contained tap water and the phosphonic acid retarderand blended per API specifications. The density of the sample was 13.6pound per gallon (ppg).

TABLE 6 Sample Composition Component % BWoRM Red Mud 100 Water 43.0Calcium Hydroxide 20.0 Weight Additive 2.0 Retarder 1.5 Dispersant 0.10

After 17 days a 5550 Chandler Viscometer was used to measure therheology of the sample in accordance with the procedure set forth in APIRP Practice 10B-2, Recommended Practice for Testing Well Cements. Thedata is presented in Table 7 below.

TABLE 7 Rheological Profile Viscosity (cP) Slurry 3 RPM 6 RPM Day 1715124 8744

After the rheological profile was obtained, the sample was split intotwo experimental samples. Experimental sample 1 was used as a controland did not include an activator/accelerator. Experimental sample 2 wasactivated and accelerated by the addition of a solution of _(——————)%calcium chloride in a sufficient amount to reach a calcium chloridecontent in experimental sample 2 of 10% BWoRM. After addition of thecalcium chloride, the compressive strengths were determined inaccordance with API RP 10B-2, Recommended Practice for Testing WellCements, First Edition, July 2005, using a FANN® ultrasonic cementanalyzer at 180° F. while maintained at 3000 psi. The compressivestrength data was measured at 1, 3, and 5 days. Note that the sample wasaged 17 days prior to curing. The compressive strength data is presentedin Table 8 below. The reported compressive strengths are an average fortwo cylinders of each sample slurry.

TABLE 8 Compressive Strengths Experimental Activator/ Day 1 C.S. Day 3C.S. Day 5 C.S. Sample Accelerator (psi) (psi) (psi) 1 — 22 32 20 2 10%BWoRM 222 240 245 CaCl₂

Example 4 illustrates that the slurry without the activator/acceleratorshowed no compressive strength development after 5 days, whereas thesample comprising the activator/accelerator was able to gains strengthover time.

It should be understood that the compositions and methods are describedin terms of “comprising,” “containing,” or “including” variouscomponents or steps, the compositions and methods can also “consistessentially of” or “consist of” the various components and steps.Moreover, the indefinite articles “a” or “an,” as used in the claims,are defined herein to mean one or more than one of the element that itintroduces.

For the sake of brevity, only certain ranges are explicitly disclosedherein. However, ranges from any lower limit may be combined with anyupper limit to recite a range not explicitly recited, as well as, rangesfrom any lower limit may be combined with any other lower limit torecite a range not explicitly recited, in the same way, ranges from anyupper limit may be combined with any other upper limit to recite a rangenot explicitly recited. Additionally, whenever a numerical range with alower limit and an upper limit is disclosed, any number and any includedrange falling within the range are specifically disclosed. Inparticular, every range of values (of the form, “from about a to aboutb,” or, equivalently, “from approximately a to b,” or, equivalently,“from approximately a-b”) disclosed herein is to be understood to setforth every number and range encompassed within the broader range ofvalues even if not explicitly recited. Thus, every point or individualvalue may serve as its own lower or upper limit combined with any otherpoint or individual value or any other lower or upper limit, to recite arange not explicitly recited.

Therefore, the present embodiments are well adapted to attain the endsand advantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, and may bemodified and practiced in different but equivalent manners apparent tothose skilled in the art having the benefit of the teachings herein.Although individual embodiments are discussed, the disclosure covers allcombinations of all of the embodiments. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. Also, the terms in the claimshave their plain, ordinary meaning unless otherwise explicitly andclearly defined by the patentee. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered ormodified and all such variations are considered within the scope andspirit of those embodiments. If there is any conflict in the usages of aword or term in this specification and one or more patent(s) or otherdocuments that may be incorporated herein by reference, the definitionsthat are consistent with this specification should be adopted.

What is claimed is:
 1. A method comprising: providing an extended-lifesettable composition comprising red mud, calcium hydroxide, water, and acement set retarder wherein the red mud is present in a redmud-to-calcium hydroxide weight ratio of about 3:1 to about 5:1 andwherein the red mud is a product of refining bauxite ore, the refiningcomprising sodium hydroxide digestion of the bauxite ore followed byfiltration of solid impurities generated by the digestion; activatingthe extended-life settable composition; introducing the extended-lifesettable composition into a subterranean formation; and allowing theextended-life settable composition to set in the subterranean formation.2. A method according to claim 1, wherein the red mud is an insolubleresidue from the refining.
 3. A method according to claim 1, wherein thewater is present in the extended-life settable composition in an amountof at least 40% by weight of the red mud.
 4. A method according to claim1, wherein the red mud comprises at least 20% calcite.
 5. A methodaccording to claim 1, wherein the cement set retarder is selected fromthe group consisting of a phosphonic acid, a phosphonic acid derivative,a lignosulfonate, a salt, an organic acid, a cellulose derivative, asynthetic co- or ter-polymer comprising sulfonate and carboxylic acidgroups, a borate compound, and any combination thereof.
 6. A methodaccording to claim 1, wherein the extended-life settable compositionfurther comprises a dispersant.
 7. A method according to claim 1,wherein the cement set retarder comprises a phosphonic acid derivative,and wherein the extended-life settable composition further comprises apolycarboxylated ether dispersant.
 8. A method according to claim 1,further comprising storing the extended-life settable composition for aperiod of 1 day or longer prior to the step of introducing the cementcomposition into the subterranean formation.
 9. A method according toclaim 1, wherein the step of activating the extended-life settablecomposition comprises adding a cement set activator to the extended-lifesettable composition.
 10. A method according to claim 1, wherein thestep of introducing the extended-life settable composition comprisespumping the extended-life settable composition through a feed pipe andinto a wellbore annulus.